1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) module, and more particularly, to an LCD module including chip-on-glass-type driving integrated circuits.
2. Discussion of the Related Art
LCD devices make use of optical anisotropy and polarization properties of liquid crystal molecules to produce images. Specifically, since the liquid crystal molecules have a definite alignment as a result of their long, thin shapes and are arranged to have initial pre-tilt angles, an alignment direction of the liquid crystal molecules can be controlled by applying an electric field. Accordingly, variations in the applied electric field influence the alignment of the liquid crystal molecules. Due to the optical anisotropy, the refraction of incident light depends on the alignment direction of the liquid crystal molecules. Thus, by properly controlling the applied electric field, an image that has a desired brightness can be produced.
An LCD device includes a liquid crystal panel for displaying images, a backlight unit for supplying the liquid crystal panel with light, and a driving unit for providing signals to the liquid crystal panel and the backlight unit.
The driving unit includes a plurality of driving integrated circuits (ICs) and printed circuit boards (PCBs). The driving ICs may be packaged to the liquid crystal panel by a tape automated bonding (TAB) method, a chip on glass (COG) method or a chip on film (COF) method.
Among the methods, in the COG method, since a chip of the driving IC is directly mounted on a substrate, a COG-type driving IC has finer pitches than other type driving ICs. Therefore, a packaging area may be minimized, and a thin device can be produced. Accordingly, the COG method has been widely used for potable devices or mobile communication devices.
A related art LCD module including a COG-type driving IC will be described hereinafter in detail with reference to FIGS. 1 and 2.
FIG. 1 is a top plan view of illustrating a related art LCD module including a COG-type driving IC. FIG. 2 is a cross-sectional view of illustrating a part of the related art LCD module and corresponding to the line II-II of FIG. 1.
In FIGS. 1 and 2, the related art LCD module includes a liquid crystal panel 10, a backlight unit 20, a driving unit 30, a case top 40, a support main 50 and a bottom cover 60.
The liquid crystal panel 10 includes a lower substrate 12 and an upper substrate 14, and a liquid crystal layer (not shown) is interposed between the substrates 12 and 14. A lower polarizer 15 is disposed under the lower substrate 12, and an upper polarizer 16 is disposed over the upper substrate 14.
The backlight unit 20 is disposed under the liquid crystal panel 10. The backlight unit 20 includes a lamp (not shown) and a plurality of optical sheets.
The driving unit 30 includes a driving IC 32 and a PCB 34. The driving IC 32 is directly mounted on the lower substrate 12 by a COG method. The PCB 32 is bent toward a rear side of the liquid crystal panel 10.
The support main 50 surrounds sides of the backlight unit 20, and the support main 50 is set on the bottom cover 60. The bottom cover 60 is combined with the case top 40 over the liquid crystal panel 10 to protect and support the liquid crystal panel 10, the backlight unit 20 and the driving unit 30.
In addition, the case top 40 covers edges of a front surface of the liquid crystal panel 10, especially, edges of a front surface of the upper polarizer 16, and exposes the front surface of the liquid crystal panel 10 through an opening. The case top 40 also covers the driving IC 32.
As stated above, the COG method has been widely used for potable devices or mobile communication devices, and for convenience of carrying, the devices have been required to get thinner and light-weighted. To do this, various methods for reducing a thickness and a weight of the LCD modules have been developed by reducing thicknesses of the upper and lower substrates 14 and 12 of the liquid crystal panel 10, a light guide panel and the optical sheets of the backlight unit 20, or elements of the driving unit 30.
As the thickness of the LCD module gets thin, the case top 40 is lowered with respect to the bottom cover 60. Therefore, distances from the case top 40 to other components of the LCD module also become short. Specially, as thicknesses of the upper substrate 14 and the upper polarizer 16 get thin, a distance between the case top 40 and the lower substrate 12 becomes short.
By the way, in the LCD module including a COG-type driving IC, since the driving IC 32 is directly mounted on the lower substrate 12 of the liquid crystal panel 10, a lower surface of the case top 40 may contact a top surface of the driving IC 32 as the thicknesses of the upper substrate 40 and the upper polarizer 16 get thin. The contact of the case top 40 and the driving IC 32 may cause cracks and wrong operation of the driving IC 32.
To prevent the driving IC 32 from contacting the case top 40, the driving IC 32 may have a thinner thickness than the related art. However, this requires an additional grinding process or a larger-sized driving IC as compared to the related art and results in increasing costs.
Alternatively, the thickness of the LCD module may be decreased by disposing an end of the case top 40 on the lower substrate 12 such that the case top 40 does not cover the driving IC 32 and exposes the upper substrate 14, the upper polarizer 16 and the driving IC 32. However, in this case, there is a problem that the LCD device cannot be protected from vibrations or impacts.